THE government has been given the go-ahead to challenge a High Court ruling that the prime minister must seek MPs' approval to trigger the process of taking Britain out of the European Union.
Permission to appeal has been granted by a panel of three justices, the Supreme Court announced on Tuesday.
In a statement, the Supreme Court said that "the case can now proceed to a full hearing".
It is expected that the proceedings will last four days beginning on December 5.
The case will be heard by all 11 Supreme Court justices.
At the completion of legal submissions, the justices will reserve their decision to a date "probably in the New Year".
It is the first time that all 11 justices will sit to hear a case.
The appeal move follows a ruling on November 3 by three High Court judges, headed by the Lord Chief Justice Lord Thomas.
On that day campaigners won their historic legal battle against Theresa May's decision to use the royal prerogative in her Brexit strategy.
In one of the most important constitutional cases in generations, the three judges ruled that the prime minister does not have power to use the prerogative to trigger Article 50 of the Lisbon Treaty to start the two-year process of negotiating Brexit without the prior authority of Parliament.
Government lawyers had argued that prerogative powers were a legitimate way to give effect "to the will of the people" who voted by a clear majority to leave the European Union in the June referendum.
But Lord Thomas declared: "The government does not have power under the crown's prerogative to give notice pursuant to Article 50 for the UK to withdraw from the European Union."
The Lord Chief Justice – sitting with the Master of the Rolls, Sir Terence Etherton, and Lord Justice Sales – emphasised to a packed court that he was deciding "a pure question of law".
"The court is not concerned with and does not express any view about the merits of leaving the European Union: that is a political issue," he said.
Prime Minister Theresa May announced at the Conservative Party conference that she intends giving an Article 50 notification by the end of March 2017.
Her opponents were "concerned citizens" drawn from all walks of life, with the lead challenge brought by investment fund manager and philanthropist Gina Miller.
Outside the Royal Courts of Justice Ms Miller was greeted by rounds of applause. Ms Miller said the result was "about our United Kingdom and all out futures. It's not about how anyone voted. Every one of us voted for the best country and the best future".
In Tuesday's statement, the Supreme Court said it had "now received formal notification of the government's intention to appeal the High Court's decision" of November 3.
It added that "permission to appeal has been granted" by a panel of three justices – Supreme Court President Lord Neuberger, Lord Mance and Lord Kerr – "and the case can now proceed to a full hearing".
The Supreme Court has set aside four days, from December 5 to 8, for the hearing.
The statement said: "The exact number of days and timings will depend on further submissions received from the parties on the precise legal arguments to be considered, the number of interveners and whether any other related cases are joined to this one.
"However, at this stage, we expect the hearing may well last all four days from Monday 5 December.
"The court can also confirm that all eleven justices will sit on the panel considering this appeal, which will be chaired by Lord Neuberger, president of the Supreme Court.
"The Supreme Court will sit in its largest courtroom and make available a live video feed in the other two courtrooms in the building to enable as many members of the public as possible to observe proceedings.
"It should be added that, as with all Supreme Court proceedings, this appeal will be live streamed on our website, so it is not necessary for people to attend the building in person to watch the hearing.
"Judgment will be reserved at the conclusion of that hearing and follow at a later date, probably in the New Year."
